/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:		arm_correlate_opt_q15.c
*
* Description:	Correlation of Q15 sequences.
*
* Target Processor: Cortex-M4/Cortex-M3
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup Corr
 * @{
 */

/**
 * @brief Correlation of Q15 sequences.
 * @param[in] *pSrcA points to the first input sequence.
 * @param[in] srcALen length of the first input sequence.
 * @param[in] *pSrcB points to the second input sequence.
 * @param[in] srcBLen length of the second input sequence.
 * @param[out] *pDst points to the location where the output result is written.  Length 2 * max(srcALen, srcBLen) - 1.
 * @param[in]  *pScratch points to scratch buffer of size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2.
 * @return none.
 *
 * \par Restrictions
 *  If the silicon does not support unaligned memory access enable the macro UNALIGNED_SUPPORT_DISABLE
 *	In this case input, output, scratch buffers should be aligned by 32-bit
 *
 * @details
 * <b>Scaling and Overflow Behavior:</b>
 *
 * \par
 * The function is implemented using a 64-bit internal accumulator.
 * Both inputs are in 1.15 format and multiplications yield a 2.30 result.
 * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
 * This approach provides 33 guard bits and there is no risk of overflow.
 * The 34.30 result is then truncated to 34.15 format by discarding the low 15 bits and then saturated to 1.15 format.
 *
 * \par
 * Refer to <code>arm_correlate_fast_q15()</code> for a faster but less precise version of this function for Cortex-M3 and Cortex-M4.
 *
 *
 */


void arm_correlate_opt_q15(
    q15_t *pSrcA,
    uint32_t srcALen,
    q15_t *pSrcB,
    uint32_t srcBLen,
    q15_t *pDst,
    q15_t *pScratch)
{
    q15_t *pIn1;                                   /* inputA pointer               */
    q15_t *pIn2;                                   /* inputB pointer               */
    q63_t acc0, acc1, acc2, acc3;                  /* Accumulators                  */
    q15_t *py;                                     /* Intermediate inputB pointer  */
    q31_t x1, x2, x3;                              /* temporary variables for holding input1 and input2 values */
    uint32_t j, blkCnt, outBlockSize;              /* loop counter                 */
    int32_t inc = 1;                               /* output pointer increment     */
    uint32_t tapCnt;
    q31_t y1, y2;
    q15_t *pScr;                                   /* Intermediate pointers        */
    q15_t *pOut = pDst;                            /* output pointer               */
#ifdef UNALIGNED_SUPPORT_DISABLE

    q15_t a, b;

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

    /* The algorithm implementation is based on the lengths of the inputs. */
    /* srcB is always made to slide across srcA. */
    /* So srcBLen is always considered as shorter or equal to srcALen */
    /* But CORR(x, y) is reverse of CORR(y, x) */
    /* So, when srcBLen > srcALen, output pointer is made to point to the end of the output buffer */
    /* and the destination pointer modifier, inc is set to -1 */
    /* If srcALen > srcBLen, zero pad has to be done to srcB to make the two inputs of same length */
    /* But to improve the performance,
     * we include zeroes in the output instead of zero padding either of the the inputs*/
    /* If srcALen > srcBLen,
     * (srcALen - srcBLen) zeroes has to included in the starting of the output buffer */
    /* If srcALen < srcBLen,
     * (srcALen - srcBLen) zeroes has to included in the ending of the output buffer */
    if(srcALen >= srcBLen)
    {
        /* Initialization of inputA pointer */
        pIn1 = (pSrcA);

        /* Initialization of inputB pointer */
        pIn2 = (pSrcB);

        /* Number of output samples is calculated */
        outBlockSize = (2u * srcALen) - 1u;

        /* When srcALen > srcBLen, zero padding is done to srcB
         * to make their lengths equal.
         * Instead, (outBlockSize - (srcALen + srcBLen - 1))
         * number of output samples are made zero */
        j = outBlockSize - (srcALen + (srcBLen - 1u));

        /* Updating the pointer position to non zero value */
        pOut += j;

    }
    else
    {
        /* Initialization of inputA pointer */
        pIn1 = (pSrcB);

        /* Initialization of inputB pointer */
        pIn2 = (pSrcA);

        /* srcBLen is always considered as shorter or equal to srcALen */
        j = srcBLen;
        srcBLen = srcALen;
        srcALen = j;

        /* CORR(x, y) = Reverse order(CORR(y, x)) */
        /* Hence set the destination pointer to point to the last output sample */
        pOut = pDst + ((srcALen + srcBLen) - 2u);

        /* Destination address modifier is set to -1 */
        inc = -1;

    }

    pScr = pScratch;

    /* Fill (srcBLen - 1u) zeros in scratch buffer */
    arm_fill_q15(0, pScr, (srcBLen - 1u));

    /* Update temporary scratch pointer */
    pScr += (srcBLen - 1u);

#ifndef UNALIGNED_SUPPORT_DISABLE

    /* Copy (srcALen) samples in scratch buffer */
    arm_copy_q15(pIn1, pScr, srcALen);

    /* Update pointers */
    //pIn1 += srcALen;
    pScr += srcALen;

#else

    /* Apply loop unrolling and do 4 Copies simultaneously. */
    j = srcALen >> 2u;

    /* First part of the processing with loop unrolling copies 4 data points at a time.
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(j > 0u)
    {
        /* copy second buffer in reversal manner */
        *pScr++ = *pIn1++;
        *pScr++ = *pIn1++;
        *pScr++ = *pIn1++;
        *pScr++ = *pIn1++;

        /* Decrement the loop counter */
        j--;
    }

    /* If the count is not a multiple of 4, copy remaining samples here.
     ** No loop unrolling is used. */
    j = srcALen % 0x4u;

    while(j > 0u)
    {
        /* copy second buffer in reversal manner for remaining samples */
        *pScr++ = *pIn1++;

        /* Decrement the loop counter */
        j--;
    }

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

#ifndef UNALIGNED_SUPPORT_DISABLE

    /* Fill (srcBLen - 1u) zeros at end of scratch buffer */
    arm_fill_q15(0, pScr, (srcBLen - 1u));

    /* Update pointer */
    pScr += (srcBLen - 1u);

#else

    /* Apply loop unrolling and do 4 Copies simultaneously. */
    j = (srcBLen - 1u) >> 2u;

    /* First part of the processing with loop unrolling copies 4 data points at a time.
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(j > 0u)
    {
        /* copy second buffer in reversal manner */
        *pScr++ = 0;
        *pScr++ = 0;
        *pScr++ = 0;
        *pScr++ = 0;

        /* Decrement the loop counter */
        j--;
    }

    /* If the count is not a multiple of 4, copy remaining samples here.
     ** No loop unrolling is used. */
    j = (srcBLen - 1u) % 0x4u;

    while(j > 0u)
    {
        /* copy second buffer in reversal manner for remaining samples */
        *pScr++ = 0;

        /* Decrement the loop counter */
        j--;
    }

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

    /* Temporary pointer for scratch2 */
    py = pIn2;


    /* Actual correlation process starts here */
    blkCnt = (srcALen + srcBLen - 1u) >> 2;

    while(blkCnt > 0)
    {
        /* Initialze temporary scratch pointer as scratch1 */
        pScr = pScratch;

        /* Clear Accumlators */
        acc0 = 0;
        acc1 = 0;
        acc2 = 0;
        acc3 = 0;

        /* Read four samples from scratch1 buffer */
        x1 = *__SIMD32(pScr)++;

        /* Read next four samples from scratch1 buffer */
        x2 = *__SIMD32(pScr)++;

        tapCnt = (srcBLen) >> 2u;

        while(tapCnt > 0u)
        {

#ifndef UNALIGNED_SUPPORT_DISABLE

            /* Read four samples from smaller buffer */
            y1 = _SIMD32_OFFSET(pIn2);
            y2 = _SIMD32_OFFSET(pIn2 + 2u);

            acc0 = __SMLALD(x1, y1, acc0);

            acc2 = __SMLALD(x2, y1, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            acc1 = __SMLALDX(x3, y1, acc1);

            x1 = _SIMD32_OFFSET(pScr);

            acc0 = __SMLALD(x2, y2, acc0);

            acc2 = __SMLALD(x1, y2, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x1, x2, 0);
#else
            x3 = __PKHBT(x2, x1, 0);
#endif

            acc3 = __SMLALDX(x3, y1, acc3);

            acc1 = __SMLALDX(x3, y2, acc1);

            x2 = _SIMD32_OFFSET(pScr + 2u);

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            acc3 = __SMLALDX(x3, y2, acc3);

#else

            /* Read four samples from smaller buffer */
            a = *pIn2;
            b = *(pIn2 + 1);

#ifndef ARM_MATH_BIG_ENDIAN
            y1 = __PKHBT(a, b, 16);
#else
            y1 = __PKHBT(b, a, 16);
#endif

            a = *(pIn2 + 2);
            b = *(pIn2 + 3);
#ifndef ARM_MATH_BIG_ENDIAN
            y2 = __PKHBT(a, b, 16);
#else
            y2 = __PKHBT(b, a, 16);
#endif

            acc0 = __SMLALD(x1, y1, acc0);

            acc2 = __SMLALD(x2, y1, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            acc1 = __SMLALDX(x3, y1, acc1);

            a = *pScr;
            b = *(pScr + 1);

#ifndef ARM_MATH_BIG_ENDIAN
            x1 = __PKHBT(a, b, 16);
#else
            x1 = __PKHBT(b, a, 16);
#endif

            acc0 = __SMLALD(x2, y2, acc0);

            acc2 = __SMLALD(x1, y2, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x1, x2, 0);
#else
            x3 = __PKHBT(x2, x1, 0);
#endif

            acc3 = __SMLALDX(x3, y1, acc3);

            acc1 = __SMLALDX(x3, y2, acc1);

            a = *(pScr + 2);
            b = *(pScr + 3);

#ifndef ARM_MATH_BIG_ENDIAN
            x2 = __PKHBT(a, b, 16);
#else
            x2 = __PKHBT(b, a, 16);
#endif

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            acc3 = __SMLALDX(x3, y2, acc3);

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

            pIn2 += 4u;

            pScr += 4u;


            /* Decrement the loop counter */
            tapCnt--;
        }



        /* Update scratch pointer for remaining samples of smaller length sequence */
        pScr -= 4u;


        /* apply same above for remaining samples of smaller length sequence */
        tapCnt = (srcBLen) & 3u;

        while(tapCnt > 0u)
        {

            /* accumlate the results */
            acc0 += (*pScr++ * *pIn2);
            acc1 += (*pScr++ * *pIn2);
            acc2 += (*pScr++ * *pIn2);
            acc3 += (*pScr++ * *pIn2++);

            pScr -= 3u;

            /* Decrement the loop counter */
            tapCnt--;
        }

        blkCnt--;


        /* Store the results in the accumulators in the destination buffer. */
        *pOut = (__SSAT(acc0 >> 15u, 16));
        pOut += inc;
        *pOut = (__SSAT(acc1 >> 15u, 16));
        pOut += inc;
        *pOut = (__SSAT(acc2 >> 15u, 16));
        pOut += inc;
        *pOut = (__SSAT(acc3 >> 15u, 16));
        pOut += inc;

        /* Initialization of inputB pointer */
        pIn2 = py;

        pScratch += 4u;

    }


    blkCnt = (srcALen + srcBLen - 1u) & 0x3;

    /* Calculate correlation for remaining samples of Bigger length sequence */
    while(blkCnt > 0)
    {
        /* Initialze temporary scratch pointer as scratch1 */
        pScr = pScratch;

        /* Clear Accumlators */
        acc0 = 0;

        tapCnt = (srcBLen) >> 1u;

        while(tapCnt > 0u)
        {

            acc0 += (*pScr++ * *pIn2++);
            acc0 += (*pScr++ * *pIn2++);

            /* Decrement the loop counter */
            tapCnt--;
        }

        tapCnt = (srcBLen) & 1u;

        /* apply same above for remaining samples of smaller length sequence */
        while(tapCnt > 0u)
        {

            /* accumlate the results */
            acc0 += (*pScr++ * *pIn2++);

            /* Decrement the loop counter */
            tapCnt--;
        }

        blkCnt--;

        /* Store the result in the accumulator in the destination buffer. */
        *pOut = (q15_t) (__SSAT((acc0 >> 15), 16));

        pOut += inc;

        /* Initialization of inputB pointer */
        pIn2 = py;

        pScratch += 1u;

    }


}

/**
 * @} end of Corr group
 */
